It is desirable to decrease the malfunction rate of firearms, for example, bolt action rifles fed ammunition from rotary magazines. Some malfunctions are attributable to the characteristics of the magazine. An example prior art magazine 11 is shown in FIG. 1. Tests indicate that sources of firearm malfunction include the top cartridge 13a not being biased by the follower 15 sufficiently against the magazine lips 17, thereby allowing the cartridge to be forced back down into the magazine in response to inertial forces caused by recoil or by application of force by the rifle bolt during feeding. Some cartridges become trapped within the magazine as a result and are prevented from engaging the feed lips. Trapped cartridges are out of position for feeding upon cycling of the bolt and may cause a malfunction. Another malfunction is caused by top cartridge 13a slipping down the follower 15 away from the magazine lips 17. Even relatively small slippage may allow the bolt to override the top cartridge and not feed properly. Some malfunctions are believed rooted in the engagement between the follower and the last cartridge 13b, where it is observed that the force vector 19 between the follower 15 and the last cartridge 13b appears not to be in the most advantageous direction to urge the cartridges into engagement with the magazine lips 17. There is an opportunity to improve the reliability of firearms, particularly bolt action rifles, by improving the characteristics of the ammunition magazine.